1. Field of the Invention
The present invention relates to structural members used in the construction of floor, roof and sides of buildings or the like and, more particularly, to bolted joists and a method of manufacturing the same.
2. Description of the Prior Art
Since the 1950""s, open web metal joists are often used in the construction of floors and roofs for commercial, industrial and residential buildings. Such open-web joists are generally formed of metal chords interconnected by metal webs. The opposed ends of the metal webs are generally welded to corresponding ones of the chords by an imposing number of welders who assemble each joist manually with the help of jigs. This manufacturing process requires specialized labor and is relatively expensive.
Trust girders having bolted connections are known in the art. For instance, U.S. Pat. No. 513,187 issued on Jan. 23, 1894 to Joly discloses a trust girder comprising upper and lower chords interconnected by means of a succession of tubular vertical members and diagonal members having angularly extending foot portions. Tie rods extend through the tubular members, the foot portions of the diagonal members and through the chords. Nuts are threadably engaged on the threaded ends of the rods to secure the chords, the vertical and diagonal members together.
It is therefore an aim of the present invention to provide a new bolted metal joist which avoids the drawbacks of known welded metal joists.
It is also an aim of the present invention to provide a novel method for manufacturing metal joists.
It is a further aim of the present invention to provide a metal joist which is relatively strong and yet lightweight.
It is a still further aim of the present invention to provide a bolted metal joist which is relatively simple and economical to manufacture.
It is a still further aim of the present invention to provide a metal joist which can be conveniently shipped in a minimum of space.
Therefore, in accordance with the present invention, there is provided a joist comprising lower and upper vertically spaced-apart chords rigidly interconnected by a succession of tension and compression webs extending between the chords, each said compression web having lower and upper angularly extending flat end portions which are respectively independently bolted to a top surface of said lower chord and an angularly extending lower flat end portion of an adjacent one of said tension webs, and to an undersurface of said upper chord and an angularly extending upper flat end portion of another adjacent one of said tension webs.
In accordance with a further general aspect of the present invention, there is provided a joist comprising upper and lower vertically spaced-apart chords rigidly interconnected by a succession of tension and compression webs extending between the chords, said upper and lower chords being each formed of a pair elongated strips having substantially L-shaped cross-sections, said strips having parallel spaced-apart vertical legs and opposed horizontal legs, said vertical legs having a plurality of longitudinally spaced-apart holes defined therein, said tension and compression webs having opposed lower and upper flat end portions respectively received between said vertical legs of said upper chord and said lower chord, each said compression web having first and second holes respectively defined in said upper and lower flat end portions thereof, said first hole being in registry with a corresponding hole defined in said upper flat end portion of an adjacent tension web and corresponding holes in said vertical legs of said upper chord for receiving a bolt, said second hole being in registry with a corresponding hole defined in said lower flat end portion of another adjacent tension web and corresponding holes in said vertical legs of said lower chord for receiving a bolt.
In accordance with a further general aspect of is the present invention, there is provided a method of manufacturing joists comprising the steps of: providing a plurality of chords, advancing said chords in a substantially continuous manner to a die punch station where holes are defined in said chords at specific locations therealong according to a predetermined pattern, advancing said chords from said die punch station to a selected one of a shipping station and an assembly station, providing a plurality of elongated webs, advancing said webs in a substantially continuous manner to a forming station where said webs are flattened at opposed end portions thereof and where holes are defined at specific locations in said opposed end portions, advancing said webs from said forming station to a selected one of said shipping station and an assembly station, and assembling metal joists by bolting pairs of prefabricated chords with prefabricated webs.